Fuse integrity indicator



D c. 24, 1940. G MAR 2225912 FUSE INTEGRITY INDICATOR Filed May 1'7, 1935 INVENTOR Y fm ii fi Patented Dec. 24, 1940 UNITED STATES PATENT OFFICE 2,225,912 FUSE'INTEGRITY INDICATOR Frank G. La Mar, New York, N. Y. Application May 17, 1935, Serial No. 21,950 '1 8 Claims.

This invention relates to electrical fuses, especially to electrical fuses of the cartridge type, and more particularly to an indicator for such fuses which acts to give information as to the 5 integrity of the fusible element.

It is well understood by those skilled in the electrical art that safety requires that all circuits which carry, or are capable of carrying, an appreciable amount of current shall have inl serted therein safety devices 1701 prevent an excessive flow of current under abnormal conditions.

A common safety device is the well-known fuse made of a strip of metal which will melt upon the flow therethrough of an undesirably heavy 15 current.

Fuses are made of many forms, amongst which the cartridge fuse is a common form. The cartridge fuse may be either of the ferrule type or of the knife blade type. In either case, it is 20 desirable to provide a convenient and simple form of means adapted to indicate the fact that the fusible metal has melted without making it necessary to first remove the fuse from its position and to disassemble the fuse.

25 It is also desirable to provide a means by which the cartridge can be readily removed manually from the supporting structure, and restored thereto without making it necessary to insert the operator's hand between the contact clips, or in 30 proximity thereto, which is of course very dangerous when a current of high voltage is flowing in the working circuit protected by the fuse.

An object of the invention is to provide an indicator device formed as a hollow body of in- 35 sulating material enclosing an indicator lamp visible through anorifice in said body and which serves also as a fuse-puller by which the cartridge may be moved bodily into and out of its supporting clip; also to provide metal connecting devices 40 for interconnecting the lamp and cartridge electrically and mechanically, whereby the indicator lamp is included in shunt with the cartridge in the working circuit when the cartridge is assembled therewith in said clips. The removal of the 45 cartridge from the contact terminal clips can also be effected conveniently by means of the integrity-indicator when constructed suitably for that purpose.

An important object of the invention is to pro- 50 vide an integrity-indicator in which extension terminals comprising metal clips which serve to interconnect the indicator means electrically with the ferrules at the ends of a cartridge fuse, so that the indicator will be in shunt to the fuse,

55 and which also serve to connect the fuse puller mechanically with the cartridge, will be so disposed that only those parts which contact with the fuse-cartridge-ends, to carry current thereto, will be exposed, and that to. a minimum extent, the rest of these connecting members being insulated. 1

A cognate object of the invention is to encase in the insulating structure of the hollow integrityindicator body as much as possible of the currentcarrying :parts, so that there is substantially no metal exposed beyond the mutually contiguous regions of the indicator tube and the fuse, nor beyond-the line of contact extending lengthwise therebetwe'en; and the invention provides also at the ends of the tube for protection of the end parts '15 by insulating material, in order to close-in the contained current-carrying parts at that region.

A further object of the invention is to provide an improved means for mounting the indicator lamp in the tubular insulatingsupport and for f completing the electrical connections between the indicator lamp, its associated resistance, and the connecting prongs or exterior terminals by which the indicator is coupled mechanically and electrically to the fuse cartridge.

Still another object of this invention is the provision of a means by which the integrity of the fusible element of a fuse may be ascertained by a visual inspection without disassemblingthe fuse or disturbing the position thereof, and which may-" be applied to the common forms of ferrule type fuses, or fuses including a ferrule or cap, by a simple manual operation,- not involving permanent fastening means. i

' Other. objects and advantages will appear asthe description of the particular physical embodiment selected to illustrate the invention progresses and the novel features of the invention will be particularly pointed out in the appended claims. In describing the invention in detail and 11161 40 particular physical embodiment selected to illustrate the invention, reference will be had to the accompanying drawing, and the several views thereof, wherein like characters of reference designate corresponding parts, and in which:

Fig. 1 is a side elevational view of a complete cartridge fuse assembly including part of a fusesupporting structure with a pair of circuit-terminal clips; and a ferrule type of fuse mounted therein, as in use, with an integrity indicator of my invention applied thereto, some parts being shown in section to illustrate the invention more clearly; I

Fig. 2 is an end-view of the device as shown in Fig. 1; I I

Fig. 3 is a fragmentary, detail view in transverse section on an enlarged scale, taken on the vertical plane indicated by the line III-III of Fig. 1, the arrows at the end of the line indicating the direction in which the view is taken;

Fig. 4 is a similar fragmentary detail view in vertical section on the median longitudinal plane of the indicator tube;

Fig. 5 is a similar transverse vertical section on the line V-V of Fig. 1;

Fig. 6 is a side elevational view of the instrumentalities illustrated in Figs. 1 and 2, but with the ferrule type fuse and its indicator partly removed from the end contact clips, which are shown in section;

Fig. '7 is a detail view in perspective of a lampsupporting part to be described;

Figs. 8, 9, and 10 are detail views in perspective, on an enlarged scale, each showing a component of one of the metal connecting end-clips or terminals, the three views showing the parts in substantially their relative positions for assembly in the final structure.

In Fig. 1, numeral I designates an ordinary and well-known form of cartridge fuse of the ferrule type. The ferrules, one at each end, are designated 2 and 3. These ferrules are metallic and conduct electricity.

As an indicator, applicant preferably employs a lamp, as 4. This lamp may be of the ordinary filament type, but preferably is of a distinctive indication type, such for instance as the discharge type, and most appropriately of the neon filled discharge type so that the color of the light is distinctive, that is, giving a distinctive and attention-arresting indication when lighted.

The lamp 4 selected for illustration is of the ordinary neon-filled discharge type having two electrodes 5 and 6. One electrode is connected by the insulated conductor 7 to a metallic end cup or bushing 8. The other terminal is connected by means of a conductor 9, a resistance I0, and a conductor I I to a metallic end cup or bushing I 2.

The metallic end bushings 8 and I2, are fitted snugly into an insulating tube I3 in which an orifice I4 is provided to allow the light to be seen. Their structure will be described more in detail hereinafter.

In pursuance of the invention, I provide each of the metallic end bushings 8 and I2 with a metallic exterior terminal or connecting device so that the indicator and the cartridge fuse are interconnected electrically and mechanically. Thus the bushing 8 has a metallic spring member I5 connected thereto and adapted to bear against the metallic end ferrule 2 of the cartridge, while metallic bushing I2 has a metallic spring member I6 connected thereto}, and bearing against the metallic cartridge ferrule 3. In addition to bearing against the metallic ferrules, each of the spring fingers may have a small approximately right angle bend I1 therein so that it will engage the lower edge as shown, of the ferrule 2 or 3, as the case may be, thus preventing the indicator from shaking off, the fuse when the fuse is placed in a vertical position.

In order to aid further the attachment of the indicator to the ferrule, the bent-over portion I1, if such is provided, may be made like a claw, with slightly separated talons to conform to the peripheral curve of the ferrule as shown in Fig. 2. The integrity indicator thus constitutes an entity which comprises the hollow body I3, and the parts associated therewith, viz., the lamp 4, resistance Ill and conductors I, 9 and I I, all contained within the body I3, and the two exterior terminals or connecting devices I5 and I6, each including a bushing as 8, I2, and a spring claw, as I1, so that this integrity-indicator-fuse-puller forms a new article of manufacture that can be manufactured and sold for application to existing cartridge fuses of the known ferrule type, as I. It will, of course, be understood that the provision of fuse-pulling means is not intended to exclude the embodiment of the other improvements herein disclosed in an integrity indicator not so adapted for use as a fuse-puller, my claim being generic to the integrity indicator unless specifically directed to other features of the invention.

In order to apply the integrity indicator to a cartridge fuse I, the latter is grasped in one hand and the integrity indicator in the other hand, and one end ferrule of the cartridge as 3 is inserted between the finger I1 and the nipple I2 and pressed in until it is engaged snugly with the part I8.

At the same time the operator pushes the other finger I! of the member I5 outwardly, to give clearance for seating of the end-ferrule 2 of the cartridge into the position shown in Fig. 6, and the indicator device is ready to act to move the cartridge into its seat between the conventional spring clips I8 and I9, which are secured as by screws 20 to a suitable supporting structure S of which a fragment is shown in the drawings.

The clips I8 and I9 are of the type adapted to serve as contact-terminals for the fuse in a working electrical circuit (not shown) in which these contact-terminals are included and which circuit is to be protected by the fuse I in known manner.

To complete the assembly of the fuse cartridge I, and its integrity indicator I3 with the clips I8 and I9, it is only necessary to press down on the hollow body I3 from the position shown in Fig. 6 and the ferrules 2 and 3 will spread the clips I8 and I 9, and then be held between the curved portions 2! thereof, while the ends ll of the metal connector strips I5 and I6 will be disposed each between two opposed knees 22, as shown in Fig. 2.

Preferably each clip will have one or more projections or lugs 23 disposed transversely of the axis of the cartridge, so that there can be no longitudinal displacement of the cartridge relatively to the clips, and thus a good contact between the clips I 8 and I9 and the ferrules 2 and 3 is assured.

The above provision also acts to prevent withdrawal of the cartridge without withdrawing the indicator member when the cartridge is withdrawn,

and then only in the intended direction, viz.,'

straight up from the support, nor can the indicator be removed from the cartridge fuse until the cartridge has been pulled out of the clips; and furthermore, the cartridge fuse can not be disassembled to permit access to the enclosed fusible element until the complete withdrawal of the cartridge fuse first from the clips and then from between the members I5 and I6 of the fuse-puller. After such withdrawal, one of the ferrules, 2 or 3 as the case may be, can be removed from the cartridge I and the enclosed fusible element withdrawn for inspection and/or replacement in the usual fashion.

The invention is particularly directed to the provision of certain other important and novel features of construction by which I have provided an integrity indicator and/or fuse-puller unusually free from exposure of current-carrying parts at any portion of its superficies, except for the projection of so much of the prong or connecting members as is necessary to effect the electrical and mechanical coupling of the indicator-carrying tube to the end ferrules of the fuse cartridge.

While there maybe considerable variation in the construction of the means by which this freedom from undesirable exposure of current-carrying parts may be secured, I have found that the structure of the various co-operating components illustrated in the drawing possesses desirable advantages, and the reason for this will be evidenced by the following description.

Reference has been made briefly to the cupshaped metal bushings 8 and I2, and to the associated terminal prongs or clip members l5 and IB. As the bushed structure at one end may be substantially identical with that at the other end, in essential respects, and as these end members are symmetrically disposed upon the ends of the tube ii], a description of the components shown at the right-hand end of Figs. 1 and 6, and illustrated in detail in all of the other figures, will suffice to make clear the now-preferred illustrative structure of each.

Each end connector comprises, in the instance illustrated, one of the cup-shaped metal bushing components, as 8 or l2, the member 8 being shown in perspective in Fig. 8, from which it will be seen that the face 24 of this bushing is desirably smooth and fiat, thus affording a good surface for uniting metallically thereto, as by sweating, the annular end 26 of one of the terminal prongs or clip members, such as shown in'Fig. 9, the latter being preferably made of sturdy strip metal, as already indicated, and which may desirably be somewhat springy.

A central hollow boss 25 on the face24 of this bushing is designed to fit snugly into a central orifice 21 in the end 26 of the clip member, and smaller orifices 28 are preferably provided therein and in the end wall 24 of the bushing, adapted to register with a similar orifice 23 in a plug member 29, shown in Fig. 10, and which is made of insulating material; and is eventually secured in place against, and in position to insulate, the outer face 30 of part 25, when the bushing 8 and part 26 of clip member 11 have been assembled with each other and the parts so assembled have been inserted within the appropriate hollow end of tube 13, as shown in Fig. 4.

The last named view shows a fastening means 3|, taking the form of a drive-screw, entering the orifices 28, andfastening the components 8, 26, 29 together securely. A similar drive-screw 32 is shown in Fig. 4 to secure the bushing 8 snugly in its inserted position, this screw passing through the wall 33 of the tube into the contiguous wall 34 of the bushing 8.

Prior to the assembly of the components at one end, it is desirable to complete the electrical connection, to the bushing 8, of the appropriate electrical conductor, as I or I I, each of which leads to its bushing, respectively extending from the electrode 5 of the lamp and from the associated resistance In. Each of these conductors may be in part at least of the heat-proof insulated type known to the electrical art as spaghetti, and each has a bare end, as 3'1, 38, only the former being described in detail as they are alike in construction and function when connected up in the following manner:

As shown in Fig. 4, the end 3] of conductor 1 is inserted into the central bore 40 of the hollow boss 25 (see Figs. 8, 4 and 5), and is there secured, as by solder S, which desirably fills the annular space between the wire and the surrounding wall of the boss, and also forms a conductive layer over the outer end of the boss, as shown clearly in Fig. 4 and in Fig. 5, thus completing very effectively the electrical connection between the indicator lamp and/or the resistance ID, as the case may be, and

been connected-in to bushing 8 in the manner already described, and the parts are in the relative positions shown in Figs. 4 and 1, i. e., so far as the bushing 8, conductor 1, indicator lamp 4, wire 9, resistance l0 and conductor H are concerned, it being understood that the bare end 38 of the conductor 33 has not yet been connected in to its bushing l2, but has been left long enough to permit manipulation thereof outside of the tube l3.

Assuming that the bushing 12 and member l5 have been sweated together, and are in hand, the operative will approach the open end of bushin 12 to the open end of tube I3 which it is to enter; will thread conductor end 38 into and through hollow boss orifice 40 in bushing l2; will introduce thebushing I 2 and part 26 of the clip member into place; will draw out undesirable slack, and then will apply solder as before described. This mode of completing electrical connections may be used at both ends, or the first described mode may be so used at both ends.

When the end connections have been completed, so far as the mechanical and electrical connections are concerned, I prefer to complete the insulation thereof by inserting the insulating plug 29 at each end, covering up the part or face 30, so that, as shown in Fig. 2, there is no metal exposed below the horizontal plane passing through the longitudinal axis of the indicator tube [3, and this arrangement carries into effect the important earlier stated object of the invention, via, to obviate all possible exposure of current carrying parts.

The aforesaid object has been accomplished to ing its strength.

1 I prefer tomake provision for supporting with an unusual degree of solidity the indicator lamp or its equivalent indicating means, in easily v sible position adjacent to the observation orifice l4, and preferably biased against the walls 3 of the tube [3 in the vicinity of said orifice l4, and I have accomplished this earlier stated object of the present invention by the provision of a. bracket-like member or auxiliary support 44, this ref- .erence character being applied to a flat shank portion of the bracket, which is designed to be introduced between the exterior wall of the bushing or of the prong-head as at 2B in Fig. 5, and the circumjacent wall of the tube l3, as indicated clearly in that figure and also in Fig. 3, the general arrangement of these parts being also shown in Figs. 1 and 4. The latter figures illustrate the manner of use of the offset supporting and 45 of this bracket, which has preferably on orifice 46 suitably disposed to receive the tip 4'! usually found at one end of this type of lamp.

By showing the lamp as arranged with this tip directed toward the middle of the tube l3 and its butt end supported by conductor 1 it is not intended to exclude the arrangement of the bracket in such a manner as to permit the support of the lamp with its tip extended toward the adjacent end of the tube 13 or in any other suitable position in this or any other suitable form of tube supporting structure in which such a. bracket may be usefully employed by reason of the nature of the improvements embodied therein. This device is sturdy and not subject to easy deformation in use, so that it prevents such injury to the indicator parts as has heretofore resulted from casual shocks in transit or in use, and from the vibrations of the supporting structure often encountered, as on ships, trains, etc. Moreover, the bracket is capable of a moderate degree of flexure, which both renders it capable of accommodation to the confined spaces Within the tube, and permits slight compensatory yielding to the displacements due to inertia of the lamp and its associated parts contained in the tube, when the tube is dropped. These displacements arise in large measure from the preferably isolated arrangement of the resistance [8, etc., and I am the first to make provision to countervail such adventitious displacements in the manner shown, or by any equivalent means.

From the foregoing it will be apparent that I have provided, in a. novel, compact and sturdy form, an integrity indicator which is easy to handle and which may also be used effectively as a means for moving the cartridge fuse into and out of its useful position relatively to the contactterminal clips.

It is also evident that the cartridge fuse assembly has a very high safety coefficient for the reason that any disassembly of the parts must be accomplished according to a pro-determined safe routine, and until the cartridge-fuse shall have been removed the indicator lamp will afford continuously an attention-arresting indication of any abnormal flow of current.

Should such an abnormal condition of flow be present when the cartridge is inserted by the use of the fuse-puller in its capacity as a pusher, that abnormal condition will be at once signalled in a manner that will infallibly arrest the attention of the operator, and that is not dependent upon a subsequent operation to be performed by the operator, so that there is no danger of careless insertion of a defective cartridge.

Moreover, as already stated to be an important feature of the invention, the removal of the cartridge I can be effected conveniently by grasping the tubular member I3 easily, and without any need for inserting the operators fingers between the contact clips [8 and I9, or in dangerous proximity thereto.

Although I have particularly described several particular embodiments of my invention and explained the principle, construction, and mode of operation thereof, nevertheless, I desire to have it understood that the forms selected are merely illustrative but do not exhaust the possible physical embodiments of the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. A fuse-integrity-indicator of the class described, characterized by an integrity-indicating means carried visibly within an elongated, hollow body of insulating material, and end members for interconnecting said indicating means electrically with the end-ferrules of a cartridge fuse, and for coupling said hollow body mechanically to said fuse, said connecting members being formed as exterior terminals comprising metal prongs projecting from each end of said hollow body at right angles thereto, and an insulating plug at each end of the tube covering the inserted end of one of said prongs so that all contiguous currentcarrying parts of the prongs at each end of the tube are insulated, and means for holding said plugs in place.

2. A fuse-integrity-indicator of the class described, comprising an integrity-indicating means carried visibly within an elongated, hollow, substantially cylindrical body of insulating structure, and flat metal prongs of resilient metal protruding in a substantially radial direction from said body in spaced parallelism relatively to each other, each near one of the ends of said body, but within planes defined by the ends of said hollow body, and insulating means covering each end of said hollow body whereby said ends present insulated extremities free from current-carrying parts of said connecting members.

3. In a fuse-integrity-indicator characterized by a hollow insulating body enclosing an electrically energized fuse-integrity-indicating means provided with flexible electrical terminal conductors having bare ends, an extension terminal for each end of said body, each of said extension terminals comprising a metal bushing component having a head with a hollow boss, and a stripmetal component having a flat head with a body aperture adapted to receive said hollow boss, said heads in each terminal being secured together metallically in nested relation, with a bare end of one of said flexible conductors secured metallically in said hollow boss.

4. A strip-metal exterior electrical terminal component for a combined fuse-integrity-indicator and fuse-puller, said metal strip having a bent-over claw divided to form talons adapted to be engaged in spaced relation with the arcuate periphery of a fuse ferrule.

5. In a fuse-integrity-indicator characterized by a hollow insulating body having an end-opening, a bushing fixed in said opening, and a fuse integrity-indicating means encased within said hollow body, a bracket member having a shank adapted to be embraced firmly between the adjacent walls of said hollow body and bushing, said bracket having an offset portion engaged with a complemental part of said indicating means, and said bracket serving as a support for said means.

6. A fuse-integrity-indicator characterized by a hollow elongated insulating body; an electrically energizable indicating means, having terminals mounted within said body, and adapted to furnish a fuse-integrity indication observable exteriorly of said body; and a pair of exterior extension electrical terminals, supported by, and projecting from, said body, one near each end thereof, for coupling said indicator mechanically and electrically with end portions of a cartridge fuse; each of said exterior terminals being characterized by having a free end with a bare contact portion for engagement with a fuse end part, and by having its other end provided with a currentcarrying portion fixed rigidly within said hollow supporting body; and means to connect each of said inner current-carrying ends with an inner terminal of said indicating means, said connecting means being encased, with said inner terminals of the indicating means, and said inner ends of the exterior terminals, by insulation, whereby said indicator is substantially free from exteriorly exposed ourrent-carrying parts other than said bare contact-portions of the free exterior terminal ends.

'7. A fuse-integrity-indicator characterized by a tubular insulating body; an electrically energizable indicating means, such as a low-voltage discharge type neon gas filled lamp having electrodes and electrode-terminals mounted within said body, and adapted to furnish a fuse-integrity indication observable exteriorly of said tubular body; and a pair of exterior extension terminals, each comprising a separately formed metal strip member supported by, and projecting from, said tubular body, one near each end thereof, said exterior terminals being spaced apart suitably for coupling said indicator mechanically and electrically with end portions of a cartridge fuse; each of said exterior terminals being further characterized by having-a free end with a bare contact portion for engagement with a fuse end part, and by having its other end provided with a current-carrying portion fixed rigidly within said tubular supporting member; and means to connect each of said inner current-carrying ends with an inner terminal of said indicating means, said connecting means being encased, with said inner terminals of the indicating means, and said inner ends of the exterior terminals, by insulation whereby said indicator is substantially free from exteriorly exposed current-carrying parts other than said bare contact-portions of the free exterior terminal ends.

8. An indicator for fuses comprising a casing having a lamp compartment formed therein, a lamp in said compartment, conductor clips, means for electrically connecting said conductor clips to said lamp, said casing having recesses formed therein, tongues formed with said conductor clips and projecting within the recesses of said casing for'connecting the clips thereto and a hook formed with each conductor clip for detachably connecting the indicator to a fuse.

FRANK C. LA MAR. 

